jbauch357

If I go from the factory 28lb injectors to Bosch 30lb injectors, will I need to tune or will the PCM automagically adjust pulse/flow based on AFR readings from the O2 sensors?

Here is what I was thinking of ordering and installing - https://www.ebay.com/itm/8x-UPGRADED...AAAOSwFmRbiaA3

Backstory below for more info -

I've been trying to chase down a strange miss/stumble for the last few months, including having it to two separate race/tuning shops who also couldn't figure it out. Compression checks out good, it happens both under closed and open loop, I've also already replaced plugs / wires / coils. Fuel pump was replaced recently when the sender died and I decided to do everything while the tank was out. Took the valve covers off to make sure I don't have a cracked or broken valve spring but everything looks good. The intake manifold gaskets were also replaced not too long ago. I'm going to triple check for vacuum leaks this weekend but like everything else feel like that's a long shot.

Only mods are Calloway honker intake, long tubes / cats / xpipe and custom tune. Car makes 383 to the wheels which is well within range of the stock injectors, but we've struggled with getting enough fuel in the past and the car seems to be running on the lean side lately.

Since I'm still running the original injectors I figure that's the next step, finding a good reasonably priced set of used OE injectors has been a bit of a pain so I'm figuring go aftermarket or slightly larger OE injectors.

RockyMtC5

feeder82

Absolutely need a tune, different scale needed

RonSSNova

jbauch357

Thanks everybody, I won't change from the OE injectors.

Also I did have my stock set ultrasonic cleaned and flow tested about 10k miles / 3 years ago, one of them was stuck wide open after that and had to be replaced but the rest of them checked out. Car ran great soon as I replaced the bad one.

The issue I'm having now just came up out of nowhere. The car was running great all weekend, I parked it for a couple hours at home then went to go run some errands and it ran terrible soon as I fired it up - that was 4 months ago.

grantv

Bad gas (happens...)? Have you run through a tank since this started?

jbauch357

Yeah, I was at a quarter tank when it started, topped it off and no change. If anything it's getting worse over time.

I haven't driven it enough to even go through a tank since that top off 4 months ago, partially because it sucks to drive and partially because I'm afraid something major is wrong that more driving will just make worse. At this point I'm not making any progress so might as well drive it until something breaks, or the tank is completely dry and I can get a full fresh tank of gas.

Bill Curlee

WHAT is the fuel pressure at idle "AND" when the engine is under load. If you have an issue that causes the pressure to drop off under load, that would cause a lean condition.

Check the pressure when the engine is cruising and WOT.

Bill

jbauch357

I'll hook up my fuel pressure gauge and do a manual check this weekend, both at idle and under load.

That said when the issue started, it would only really happen under load from about 3K RPM up... below 3K RPM or not under a load and you couldn't hear/feel it.

Lately it's been getting progressively worse. Now I can feel it even under neutral throttle and it's starting to happen around 2K RPM.